CN112299888B

CN112299888B - Nano selenium nutrient solution and preparation method thereof

Info

Publication number: CN112299888B
Application number: CN202011300587.XA
Authority: CN
Inventors: 王贞婷; 卢斌; 张丁日; 梁盛华; 章云芳
Original assignee: Hangzhou Fuchun Selenium Valley Agricultural Technology Co ltd
Current assignee: Hangzhou Fuchun Selenium Valley Agricultural Technology Co ltd
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2022-09-30
Anticipated expiration: 2040-11-19
Also published as: CN112299888A

Abstract

The invention discloses a nano-selenium nutrient solution and a preparation method thereof, belonging to the technical field of animal and plant nutrient solutions. According to the preparation method of the nano-selenium nutrient solution, the selenium nano-porous hydrogel particles with the particle size distribution of 1-5 microns can be prepared, the rate of releasing sodium selenite from nano-pores of the obtained nano-selenium nutrient solution is slow and lasting, the crops can be ensured to slowly and fully absorb selenium fertilizer, and the prepared nano-selenium nutrient solution has good storage stability and does not generate agglomeration and sedimentation phenomena in the shelf life; the preparation method does not need special equipment in the preparation process, the production raw materials are simple and easy to obtain, the process can be continuous, and the method is suitable for industrial production.

Description

Nano selenium nutrient solution and preparation method thereof

Technical Field

The invention belongs to the technical field of animal and plant nutrient solutions, and particularly relates to a nano selenium nutrient solution and a preparation method thereof.

Background

Selenium is a trace element necessary for maintaining human health, and has important effects in cancer prevention, cancer resistance and oxidation resistance, but selenium can only be obtained from food, and cannot be synthesized by human body. The rapid development of the society leads the living standard and the nutrition knowledge of people to be gradually improved, and the selenium-enriched food which is green and healthy is favored by people with more attention to health care and health preservation. In order to make crops contain more selenium, people begin to use selenium-containing fertilizers, sodium selenite and other measures to produce selenium-rich crops. The sodium selenite has an obvious effect on improving the selenium content of crops and has a certain yield increase effect, but the absorption efficiency of the crops to the sodium selenite is low, the effect of enriching the selenium in the crops is not easy to achieve, and because the sodium selenite does not have a slow release effect, the sodium selenite is easy to cause harm to the crops due to excessive application, and the cost of the sodium selenite is high.

In order to reduce the damage of high-concentration sodium selenite to crops and improve the selenium content of the crops, related researchers begin to research and develop slow-release selenium-rich water fertilizers. Usually, a solid phase adsorption carrier is required to adsorb sodium selenite, but three difficulties mainly exist in utilizing the method; firstly, a solid phase adsorption carrier for adsorbing sodium selenite is easy to agglomerate, delaminate and settle in a water-fertilizer system; secondly, the adsorption quantity of the adsorption carrier is low; thirdly, the speed of releasing sodium selenite by the adsorption carrier is fast and is not easy to control. For example, the chinese patent application No. 201711394630.1 discloses a nano-selenium liquid manure solution and a preparation method thereof, which uses nano-silica as an adsorption carrier to adsorb sodium selenite, and uses xanthan gum as an anti-settling agent to suspend the nano-silica in a liquid manure system. However, as the nano-silica is a dense material, the sodium selenite is adsorbed only on the surface of the nano-silica, the adsorption quantity is very low, and the desorption rate is relatively high; and the xanthan gum in the water and fertilizer system is easy to mildew, so that the quality guarantee period of the water and fertilizer is short.

Disclosure of Invention

In order to overcome the defects of the prior art, the technical problems to be solved by the invention are as follows: provides a nano selenium nutrient solution with high adsorption quantity and low release speed of sodium selenite and a preparation method thereof.

In order to solve the technical problems, the invention adopts the technical scheme that: a method for preparing nano selenium nutrient solution comprises the following steps:

step 1, mixing water glass, water and an acid catalyst and reacting to obtain acidic silica sol with a pH value of 4.5-5.5 for later use; the mass ratio of the water glass to the water to the acid catalyst is 10: 4-8: 1.5-3.5;

step 2, dissolving sodium selenite in water to obtain a sodium selenite aqueous solution with the pH value of 13-14; the mass ratio of the sodium selenite to the water is 1: 1.5-2.8;

step 3, adding the sodium selenite aqueous solution obtained in the step 2 into the acidic silica sol obtained in the step 1, and uniformly stirring to obtain a mixed solution; the mass ratio of the acidic silica sol to the sodium selenite aqueous solution is 1: 16-22;

step 4, sequentially carrying out ultrasonic atomization and microwave radiation heating on the mixed solution obtained in the step 3 to obtain selenium-rich nano-porous hydrogel particles with the particle size of 1-5 microns;

step 5, mixing the selenium-rich nano-porous hydrogel particles obtained in the step 4, water, an anti-settling agent and a mildew preventive to obtain a nano-selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the water to the anti-settling agent to the mildew preventive is 10: 7-11: 0.01-0.15: 0.01-0.05.

The technical scheme adopted by the invention is as follows: a nano-selenium nutrient solution prepared by the preparation method of the nano-selenium nutrient solution.

The invention has the beneficial effects that: the invention provides a nano-selenium nutrient solution and a preparation method thereof.A sol-gel method is adopted to prepare a selenium-rich nano-porous hydrogel, and sodium selenite is not only filled in the nano-porous hydrogel as a selenium-rich functional phase, but also used as an alkaline catalyst to participate in sol-gel reaction; the preparation method can atomize the selenium-rich silica sol into nano-porous hydrogel particles with the particle size of 1-5 mu m, the aperture of the hydrogel particles is 15-25nm, and the hydrogel particles can play a synergistic thickening and anti-settling effect after being mixed with xanthan gum and hydroxypropyl cellulose, so that the selenium-rich nano-porous hydrogel particles are uniformly dispersed in a water-fertilizer system, and the aggregation and sedimentation phenomena are not generated in the shelf life; the rate of releasing sodium selenite from the nano-pores by the obtained nano-selenium nutrient solution is slow and durable, so that crops can slowly and fully absorb selenium fertilizer; meanwhile, the nano-selenium nutrient solution and the preparation method thereof provided by the application do not need special equipment in the preparation process, the production raw materials are simple and easy to obtain, the process can be continuous, and the nano-selenium nutrient solution is suitable for industrial production.

Drawings

FIG. 1 is an electron microscope scanning image of the nano-selenium nutrient solution prepared by the method for preparing the nano-selenium nutrient solution according to the embodiment of the invention;

FIG. 2 is an electron microscope scanning image of the nano-selenium nutrient solution prepared by the method for preparing a nano-selenium nutrient solution according to the embodiment of the present invention;

FIG. 3 is an electron microscope scanning image of wheat grains obtained after the nano-selenium nutrient solution prepared by the method for preparing a nano-selenium nutrient solution of the embodiment of the invention is applied to wheat;

fig. 4 is an electron microscope scanning image of wheat grains obtained in a clear water test of the test group 1 of application example 1 according to the embodiment of the present invention;

fig. 5 is an electron microscope scanning image of the top of corn kernel obtained by applying the nano-selenium nutrient solution prepared by the method for preparing the nano-selenium nutrient solution of the embodiment of the invention to corn;

fig. 6 is an electron microscope scan of the top of corn kernels obtained in the clear water test of test group 1 of application example 1 in accordance with the present embodiment of the invention;

fig. 7 is an electron microscope scanning image of tea leaves obtained after the nano selenium nutrient solution prepared by the method for preparing a nano selenium nutrient solution according to the embodiment of the invention is applied to tea leaves;

fig. 8 is an electron microscope scanning image of tea leaves obtained in the water test of test group 1 of application example 1 according to the embodiment of the present invention.

Detailed Description

In order to explain the technical contents, the objects and the effects of the present invention in detail, the following description is made with reference to the accompanying drawings in combination with the embodiments.

The invention relates to a preparation method of a nano-selenium nutrient solution, which comprises the following steps:

step 1, mixing water glass, water and an acid catalyst at normal temperature, and reacting to obtain acidic silica sol with a pH value of 4.5-5.5 for later use; the mass ratio of the water glass to the water to the acid catalyst is 10: 4-8: 1.5-3.5;

step 2, dissolving sodium selenite in water at normal temperature to obtain a sodium selenite aqueous solution with the pH value of 13-14; the mass ratio of the sodium selenite to the water is 1: 1.5-2.8;

step 4, sequentially carrying out ultrasonic atomization and microwave radiation heating on the mixed solution obtained in the step 3 to obtain selenium-rich nano porous hydrogel particles with the particle size of 1-5 microns;

step 5, mixing the selenium-rich nano-porous hydrogel particles obtained in the step 4, water, an anti-settling agent and an anti-mildew agent to obtain a nano-selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the water to the anti-settling agent to the mildew preventive is 10: 7-11: 0.01-0.15: 0.01-0.05.

From the above description, the beneficial effects of the present invention are: the preparation method of the nano-selenium nutrient solution provided by the invention adopts a sol-gel method to prepare the selenium-rich nano-porous hydrogel; in the sol stage, the hydrolysis reaction is carried out by using high-alkaline water glass and an acid catalyst, and Si-O is arranged on the water glass ^- Radical in H ⁺ Compared with the traditional silica sol with the pH value of 6.5-8.5, the pH value of the silica sol is adjusted to 4.5-5.5 by specifically adjusting the dosage of the acid catalyst, so that the aqueous solution of alkaline sodium selenite can be used as a gel accelerator of the acidic silica sol and is filled in the silica hydrogel as a selenium-rich functional phase, the release rate of the sodium selenite in the nanopores of the silica hydrogel is slow, the crops can be ensured to have sufficient time to slowly and fully absorb selenium fertilizer, and the damage to the crops caused by excessive application can be avoided while the growth of the crops is promoted;

according to the method, the selenium-rich nano-porous hydrogel is treated by an ultrasonic atomization process, electronic high-frequency oscillation is utilized, molecular bonds among liquid water molecules of the selenium-rich silica sol are broken up through high-frequency resonance of a ceramic atomization sheet, microwave radiation heating is adopted to shorten the gel time of an atomized body to 0.5-1min, and then the atomized body is atomized into selenium-rich nano-porous hydrogel particles with the particle size of 1-5 microns, the aperture of the selenium-rich nano-porous hydrogel particles is 15-25nm, so that the selenium-rich nano-porous hydrogel particles can be fully mixed and dispersed with water, an anti-settling agent and a mildew preventive, and the problem of settling cannot occur.

Further, the modulus of the water glass in the step 1 is 3-3.3.

As can be seen from the above description, the silica sol obtained by the water glass with the modulus of 3-3.3 has higher density, and is suitable for preparing the nano selenium nutrient solution by the method provided by the invention.

Further, in the step 1, the acid catalyst is one or more of oxalic acid, acetic acid, nitric acid and phosphoric acid.

The acid catalyst does not pollute soil after being applied, and is more environment-friendly.

Further, in the step 4, the oscillation frequency of the ultrasonic atomization is 1.7MHz, the frequency of the microwave radiation heating is 2450MHz, and the time of the microwave radiation heating is 0.5-2.5 min.

From the above description, microwave radiation heating helps to promote rapid gelation of silica sol, and 0.5-2.5min can avoid the problem that solvent evaporation is caused by too high temperature, which leads to collapse of the nano-porous structure of gel.

Further, the anti-settling agent in the step 5 is prepared from the following components in a mass ratio of 1: 1.5 of xanthan gum and hydroxypropyl cellulose.

From the above description, when the mass ratio of xanthan gum to hydroxypropyl cellulose is specifically selected to be 1: 1.5, the two are cooperated to form a three-dimensional interpenetrating network structure, which can effectively promote the suspension of the selenium-rich nano-porous hydrogel particles in the water fertilizer without agglomeration and sedimentation.

Further, in the step 5, the mildew preventive is one or more of triadimefon, prochloraz and vinclozolin.

As can be seen from the description, the mildew preventive is selected to effectively prevent the water-fertilizer system containing xanthan gum and hydroxypropyl cellulose from mildewing, and the shelf life of the obtained nano selenium nutrient solution is remarkably prolonged.

Further, in step 5: mixing the selenium-rich nano-porous hydrogel particles obtained in the step (4), a surfactant, water, an anti-settling agent and an anti-mildew agent to obtain a nano-selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the surfactant is 10: 0.01-0.1.

From the above description, when the nano-selenium water fertilizer provided by the technical scheme of the invention is used as a soil fertilizer, a surfactant is not added; when the water-fertilizer foliar fertilizer is used for foliar fertilizers, the water-fertilizer absorption amount of the leaf surfaces of crops is low due to the fact that the lotus leaf effect is easy to occur between the water-fertilizer and the leaf surfaces of the crops, and the water-fertilizer can wet the leaf surfaces of the crops after the surfactant is added, so that the liquid level of the crops can fully absorb the water-fertilizer.

Further, the surfactant is one or more of sodium butyl naphthalene sulfonate, oleic acid, sodium dodecyl benzene sulfonate and butyl alcohol stearate.

Further, in the step 3, the rotation speed of the stirring and the uniform mixing is 500-;

and step 5, mixing by adopting mechanical stirring, wherein the stirring speed is 3000-6500 r/min, and the stirring time is 5-15 min.

From the above description, the high shear rate in step 5 helps to improve the dispersion performance and avoid the agglomeration problem in the later period, and the mass ratio is 1: 1.5 Xanthan gum and hydroxypropyl cellulose are of low viscosity at high shear and have excellent working properties.

A nano-selenium nutrient solution prepared by the preparation method of the nano-selenium nutrient solution.

Example 1:

the preparation method of the nano selenium nutrient solution specifically comprises the following steps:

step 1, mixing water glass with a modulus of 3, water and oxalic acid at normal temperature, and reacting to obtain acidic silica sol with a pH value of 4.5 for later use; the mass ratio of the water glass to the water to the oxalic acid is 10: 4: 3.5;

step 2, dissolving sodium selenite in water at normal temperature to obtain a sodium selenite aqueous solution with the pH value of 14; the mass ratio of the sodium selenite to the water is 1: 1.5;

step 3, adding the sodium selenite aqueous solution obtained in the step 2 into the acidic silica sol obtained in the step 1, and uniformly stirring at the rotation speed of 1000 revolutions per minute for 1min to obtain a mixed solution; the mass ratio of the acidic silica sol to the sodium selenite aqueous solution is 1: 16;

step 4, in a closed container, carrying out ultrasonic atomization treatment on the mixed solution obtained in the step 3 by using an ultrasonic atomizer, wherein the oscillation frequency of the ultrasonic atomizer is 1.7MHz, so as to obtain an atomized body; then carrying out microwave radiation heating on the atomized body, wherein the frequency of the microwave radiation heating is 2450MHz, and the time of the microwave radiation heating is 2.5min, so as to obtain the selenium-rich nano-porous hydrogel particles with the particle size d50 of 1 mu m, wherein the pore diameter of the selenium-rich nano-porous hydrogel particles is 15-25 nm;

step 5, mechanically stirring and mixing the selenium-enriched nano porous hydrogel particles obtained in the step 4, water, the anti-settling agent and triazolone, wherein the rotating speed of mechanical stirring is 3000 r/min, and the time is 15min, so as to obtain nano selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the water to the anti-settling agent to the triazolone is 10: 7: 0.15: 0.01;

the anti-settling agent is prepared from the following components in percentage by mass of 1: 1.5 of xanthan gum and hydroxypropyl cellulose.

The nano selenium nutrient solution of example 1 is stored in a closed container, and observed after being placed for 30 days at room temperature, the aggregation and sedimentation phenomena are not generated.

Example 2:

step 1, mixing water glass with a modulus of 3.3, water and phosphoric acid at normal temperature, and reacting to obtain acidic silica sol with a pH value of 5.5 for later use; the mass ratio of the water glass to the water to the phosphoric acid is 10: 8: 1.5;

step 2, dissolving sodium selenite in water at normal temperature to obtain a sodium selenite aqueous solution with the pH value of 13; the mass ratio of the sodium selenite to the water is 1: 2.8 of;

step 3, adding the sodium selenite aqueous solution obtained in the step 2 into the acidic silica sol obtained in the step 1, and uniformly stirring at the rotation speed of 500 revolutions per minute for 2min to obtain a mixed solution; the mass ratio of the acidic silica sol to the sodium selenite aqueous solution is 1: 22;

step 4, in a closed container, carrying out ultrasonic atomization treatment on the mixed liquor obtained in the step 3 by using an ultrasonic atomizer, wherein the oscillation frequency of the ultrasonic atomizer is 1.7MHz, so as to obtain an atomized body; then carrying out microwave radiation heating on the atomized body, wherein the frequency of the microwave radiation heating is 2450MHz, and the time of the microwave radiation heating is 0.5min, so as to obtain selenium-rich nano-porous hydrogel particles with the particle size d50 of 5 mu m, wherein the pore diameter of the selenium-rich nano-porous hydrogel particles is 15-25 nm;

step 5, mechanically stirring and mixing the selenium-rich nano-porous hydrogel particles obtained in the step 4, water, the anti-settling agent and the ethephon sclerotium for 5min at the rotating speed of 6500 r/min to obtain nano-selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the water to the anti-settling agent to the ethephon sclerotium is 10: 11: 0.01: 0.05;

The nano selenium nutrient solution of the example 2 is stored in a closed container, and is observed after being placed for 30 days at room temperature, and no agglomeration and sedimentation phenomena occur.

Example 3:

step 1, mixing water glass with a modulus of 3.3, water and acetic acid at normal temperature, and reacting to obtain acidic silica sol with a pH value of 5.5 for later use; the mass ratio of the water glass to the water to the acetic acid is 10: 6: 2;

step 2, dissolving sodium selenite in water at normal temperature to obtain a sodium selenite aqueous solution with the pH value of 10.5; the mass ratio of the sodium selenite to the water is 1: 2;

step 3, adding the sodium selenite aqueous solution obtained in the step 2 into the acidic silica sol obtained in the step 1, and uniformly stirring at the rotation speed of 800 revolutions per minute for 2min to obtain a mixed solution; the mass ratio of the acidic silica sol to the sodium selenite aqueous solution is 1: 19;

step 4, in a closed container, carrying out ultrasonic atomization treatment on the mixed solution obtained in the step 3 by using an ultrasonic atomizer, wherein the oscillation frequency of the ultrasonic atomizer is 1.7MHz, so as to obtain an atomized body; then carrying out microwave radiation heating on the atomized body, wherein the frequency of the microwave radiation heating is 2450MHz, and the time of the microwave radiation heating is 1.5min, so as to obtain the selenium-rich nano-porous hydrogel particles with the particle size d50 of 4.5 mu m, wherein the pore diameter of the selenium-rich nano-porous hydrogel particles is 15-25 nm;

step 5, mechanically stirring and mixing the selenium-rich nano-porous hydrogel particles obtained in the step 4, water, an anti-settling agent, prochloraz and sodium dodecyl benzene sulfonate, wherein the mechanical stirring speed is 5000 revolutions per minute, and the time is 5 minutes, so as to obtain nano-selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the water to the anti-settling agent to the prochloraz is 10: 9: 0.01: 0.05: 0.05;

The nano selenium nutrient solution of the example 3 is stored in a closed container, and is observed after being placed for 30 days at room temperature, and no agglomeration and sedimentation phenomena occur.

Example 4:

step 1, mixing water glass with a modulus of 3.2, water and an acid catalyst at normal temperature, and reacting to obtain acidic silica sol with a pH value of 4.5 for later use; the mass ratio of the water glass to the water to the acid catalyst is 10: 5: 3, the acid catalyst is oxalic acid, phosphoric acid and a mixture;

step 3, adding the sodium selenite aqueous solution obtained in the step 2 into the acidic silica sol obtained in the step 1, and uniformly stirring at the rotation speed of 600 revolutions per minute for 1.5min to obtain a mixed solution; the mass ratio of the acidic silica sol to the sodium selenite aqueous solution is 1: 18;

step 4, in a closed container, carrying out ultrasonic atomization treatment on the mixed liquor obtained in the step 3 by using an ultrasonic atomizer, wherein the oscillation frequency of the ultrasonic atomizer is 1.7MHz, so as to obtain an atomized body; then carrying out microwave radiation heating on the atomized body, wherein the frequency of the microwave radiation heating is 2450MHz, and the time of the microwave radiation heating is 2min, so as to obtain selenium-rich nano-porous hydrogel particles with the particle size d50 of 3 mu m, wherein the pore diameter of the selenium-rich nano-porous hydrogel particles is 15-25 nm;

step 5, mechanically stirring and mixing the selenium-rich nano-porous hydrogel particles obtained in the step 4, water, the anti-settling agent and the mildew preventive, wherein the rotation speed of mechanical stirring is 4500 revolutions per minute, and the time is 10 minutes, so as to obtain nano-selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the water to the anti-settling agent to the mildew preventive is 10: 8: 0.15: 0.08, the mildew preventive is a mixture of triazolone and prochloraz;

The nano selenium nutrient solution of the example 4 is stored in a closed container, and is observed after being placed for 30 days at room temperature, and no agglomeration and sedimentation phenomena occur.

Comparative example 1:

the comparative example 1 is different from the example 1 only in that the mass ratio of the water glass added in the step 1 to the oxalic acid is 10: 5.

during the preparation process, the atomized body can not be gelatinized, and the selenium-rich nano-porous hydrogel particles can not be prepared.

Comparative example 2:

comparative example 2 differs from example 1 only in that the mass ratio of sodium selenite to water in step 2 is 1: 10.

Comparative example 3:

comparative example 3 differs from example 1 only in that no xanthan gum is added in step 5.

In the preparation process, the obtained selenium-rich nano-porous hydrogel particles cannot be uniformly dispersed in the nano-selenium water fertilizer solution, and obvious layering phenomenon occurs after 1 day.

Comparative example 4:

comparative example 4 differs from example 1 only in that no hydroxypropyl cellulose was added in step 5.

In the preparation process, the obtained selenium-rich nano-porous hydrogel particles cannot be uniformly dispersed in the nano-selenium water fertilizer solution, and obvious layering phenomenon occurs after 2 days.

Application example 1:

respectively spraying the nano-selenium nutrient solution prepared by the preparation method of example 1 in corn, wheat and Longjing tea planting areas according to the measurement of each acre every time, wherein the nano-selenium nutrient solution is sprayed by 0g (equal amount of clear water), 0.8g, 1.6g, 2.4g and 3.2g (respectively marked as a test group 1, a test group 2, a test group 3, a test group 4 and a test group 5) in terms of the mass of selenium element, wherein the wheat is sprayed twice, and the rest crops are sprayed once; after the crops are mature, the selenium content in the crops is detected, the yield increasing effect is calculated by comparing the selenium content with the components with the addition of 0g, the detection results are shown in tables 1-3, and the average value is taken.

TABLE 1

Group of	Selenium content of nano-selenium water fertilizer	Crop selenium content (mg/kg)	Effect of increasing yield
				Corn test group 1	0 g/mu	Not detected out	0
Corn test group 2	0.8 g/mu	0.13	6％
				Corn test group 3	1.6 g/mu	0.20	12.1％
Corn test group 4	2.4 g/mu	0.34	18.2％
				Corn test group 5	3.2 g/mu	0.45	13.3％

TABLE 2

Group of	Selenium content of nano-selenium water fertilizer	Crop selenium content (mg/kg)	Effect of increasing yield
				Wheat test group 1	0 g/mu	0.14	0％
Wheat test group 2	0.8 g/mu	1.90	5.1％
				Wheat test group 3	1.6 g/mu	2.51	10.4％
Wheat test group 4	2.4 g/mu	4.04	14.2％
				Wheat test group 5	3.2 g/mu	6.43	5.4％

TABLE 3

Group of	Selenium content of nano-selenium liquid fertilizer	Crop selenium content (mg/kg)	Effect of increasing yield
				Tea test set 1	0 g/mu	Not detected out	0％
Tea test set 2	0.8 g/mu	0.56	7.6％
				Tea test group 3	1.6 g/mu	0.82	14.3％
Tea test set 4	2.4 g/mu	1.15	20.2％
				Tea test set 5	3.2 g/mu	1.37	16.5％

Referring to fig. 3 and 4, fig. 3 is an electron microscope scan of wheat grains of the wheat test group 4 sprayed with 2.4g of the nano selenium nutrient solution of example 1, and fig. 4 is an electron microscope scan of wheat grains planted in clear water of the wheat test group 1, so that the wheat grains sprayed with the nano selenium nutrient solution are fuller, and the microstructure of the bottoms of the grains is more.

Referring to fig. 5 and 6, fig. 5 is an electron microscope scan of the top of corn kernels of the corn test group 4 sprayed with 2.4g of the nano selenium nutrient solution of example 1, and fig. 6 is an electron microscope scan of the top of corn kernels planted in clear water of the corn test group 1, which shows that the microstructure of the top of corn kernels sprayed with the nano selenium nutrient solution is significantly increased.

Referring to fig. 7 and 8, fig. 7 is an electron microscope scan of the longjing tea leaves of the tea test group 4 sprayed with 2.4g of the nano selenium nutrient solution of example 1, and fig. 8 is an electron microscope scan of the longjing tea leaves planted in clear water of the tea test group 1, it can be seen that the number of hairs of the longjing tea leaves sprayed with the nano selenium nutrient solution is significantly increased.

Application example 2:

adding 0mL, 0.3mL, 0.5mL, 0.8mL and 1.0mL of nano-selenium nutrient solution containing 5% of selenium into feed of every 500 laying hens per day (respectively marked as a laying hen test group 1, a laying hen test group 2, a laying hen test group 3, a laying hen test group 4 and a laying hen test group 5);

adding 0mL, 0.8mL, 1.6mL, 3.2mL and 4.8mL of nano-selenium nutrient solution containing 5% of selenium into feed of every 500 pigs per day (respectively marked as a pig test group 1, a pig test group 2, a pig test group 3, a pig test group 4 and a pig test group 5);

after 45 days, eggs laid by laying hens and after 66 days, the selenium content in the muscle of pigs are respectively compared and analyzed with the components with the addition of 0mL, the detection results are shown in tables 4-5, and the average value is taken.

TABLE 4

Group of	Daily dosage of nanometer selenium nutrient solution	Selenium content of egg (mg/kg)	Cholesterol content (mg/100g)
				Test group of laying hens 1	0mL/500 pieces	0.23	417
Laying hen test group 2	0.3mL/500 pieces	0.37	402
				Test group of laying hens 3	0.5mL/500 pieces	0.42	384
Test group of laying hens 4	0.8mL/500 pieces	0.48	376
				Test group of laying hens 5	1.0mL/500 pieces	0.64	356

TABLE 5

Group of	Daily dosage of nanometer selenium nutrient solution	Selenium content in pork (mg/kg)
			Pig test group 1	0mL/500 pieces	Is free of
Pig test group 2	0.8mL/500 pieces	0.172
			Pig test group 3	1.6mL/500 pieces	0.436
Pig test group 4	3.2mL/500 pieces	0.754
			Pig test group 5	4.8mL/500 pieces	1.13

Application example 3:

combining the experimental data of two application examples, the nano-selenium nutrient solution prepared by the preparation method of the embodiment 1-3 is taken, clear water is taken as a control group 1, a sodium selenite solution is taken as a control group 2, a nano-silica sodium selenite solution is taken as a control group 3, water is added to the nano-selenium nutrient solution respectively to prepare a fertilizer solution containing 0.05 wt% of selenium (the control group 1 contains 0 wt% of selenium), then 6 groups of planting experiments are carried out on the wheat planted in the same batch respectively, the conditions except the selenium-containing fertilizer solution in the experimental process are all the same, 2 times of spraying are carried out in the heading stage of the wheat, and the interval between the two times of spraying is 10 days. The wheat 3 rd and 7 th days after the second spraying is taken for testing, the selenium content in the sample is measured, the selenium content and the yield in the wheat after harvesting are measured, the yield increasing effect is calculated by comparing with the control group 1, and the result is shown in table 6.

TABLE 6

Among them, it was found that 99% of selenium in the test wheat of examples 1 to 3 was present in the form of organic selenium.

It can be seen from table 6 that the selenium content in wheat plants rose faster in the first seven days of fertilization, and the analysis was that the nano-porous hydrogel particles were used as the carrier, so that the selenium content absorbed and transformed by the wheat of examples 1-3 groups was higher, and from the relevant data of day 3 and day 7, the nano-selenium nutrient solution provided by the present invention released more stably on wheat and lost less, and the yield increasing effect of the nano-selenium nutrient solution on crops was more obvious by combining the selenium content and yield data of wheat during harvesting, and the selenium content enriched after plant absorption was higher.

In conclusion, the nano-selenium nutrient solution and the preparation method thereof provided by the invention adopt a sol-gel method to prepare the selenium-rich nano-porous hydrogel, and sodium selenite is not only filled in the nano-porous hydrogel as a selenium-rich functional phase, but also participates in a sol-gel reaction as an alkaline catalyst; the preparation method can prepare the selenium nano-porous hydrogel particles with the particle size distribution of 1-5 mu m, and the selenium nano-porous hydrogel particles can play a synergistic thickening and anti-settling effect after being mixed with xanthan gum and hydroxypropyl cellulose, so that the selenium-rich nano-porous hydrogel particles are uniformly dispersed in a water-fertilizer system, and the aggregation and sedimentation phenomenon is avoided in the shelf life; the rate of releasing sodium selenite from the nano-pores by the obtained nano-selenium nutrient solution is slow and durable, so that crops can slowly and fully absorb selenium fertilizer; meanwhile, the nano-selenium nutrient solution and the preparation method thereof provided by the application do not need special equipment in the preparation process, the production raw materials are simple and easy to obtain, the process can be continuous, and the nano-selenium nutrient solution is suitable for industrial production.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention and the contents of the accompanying drawings, which are directly or indirectly applied to the related technical fields, are included in the scope of the present invention.

Claims

1. A preparation method of nano selenium nutrient solution is characterized by comprising the following steps:

step 4, in a closed container, carrying out ultrasonic atomization treatment on the mixed solution obtained in the step 3 by using an ultrasonic atomizer, wherein the oscillation frequency of the ultrasonic atomizer is 1.7MHz, so as to obtain an atomized body; then carrying out microwave radiation heating on the atomized body, wherein the frequency of the microwave radiation heating is 2450MHz, and the time of the microwave radiation heating is 0.5-2.5min, so as to obtain selenium-rich nano-porous hydrogel particles with the particle size d50 of 1-5 mu m, wherein the pore diameter of the selenium-rich nano-porous hydrogel particles is 15-25 nm;

step 5, mixing the selenium-rich nano-porous hydrogel particles obtained in the step 4, water, an anti-settling agent and an anti-mildew agent to obtain a nano-selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the water to the anti-settling agent to the mildew preventive is 10: 7-11: 0.01-0.15: 0.01-0.05;

2. The method for preparing nano selenium nutrient solution as claimed in claim 1, wherein the modulus of the water glass in step 1 is 3-3.3.

3. The method for preparing nano selenium nutrient solution as claimed in claim 1, wherein the acid catalyst in step 1 is one or more of oxalic acid, acetic acid, nitric acid and phosphoric acid.

4. The method for preparing nano-selenium nutrient solution as claimed in claim 1, wherein the anti-mold agent in step 5 is one or more of triadimefon, prochloraz and vinclozolin.

5. The method for preparing nano selenium nutrient solution as claimed in claim 1, wherein the step 5 is: mixing the selenium-rich nano-porous hydrogel particles obtained in the step (4), a surfactant, water, an anti-settling agent and an anti-mildew agent to obtain a nano-selenium nutrient solution; the mass ratio of the selenium-rich nano-porous hydrogel particles to the surfactant is 10: 0.01-0.1.

6. The method for preparing nano selenium nutrient solution as claimed in claim 5, wherein the surfactant is one or more of butyl naphthalene sodium sulfonate, oleic acid, sodium dodecyl benzene sulfonate and butyl alcohol stearate.

7. The method for preparing nano-selenium nutrient solution as claimed in claim 1, wherein in step 3, the rotation speed for stirring and mixing is 500-;

8. A nano-selenium nutrient solution prepared by the method for preparing the nano-selenium nutrient solution of any one of claims 1 to 7.